In general, a liquid crystal display (LCD) refers to as a display device in which by separately supplying data signals according to image information to pixels arranged in a matrix type and adjusting light transmission rates of the pixels, images can be adjusted to desired images wherein since it does not self-emit light, a back light unit is arranged on a rear surface thereof to display images.
Referring to FIG. 1, in the back light unit 1, a flat-light guide plate 30 is arranged on a substrate 20 and a plurality of side view LEDs 10 (only one shown) are arranged as an array type on a side of the light guide plate 30.
In the LED 10, light L entered to the light guide plate 30 is reflected upwardly from fine reflection patterns or a reflection sheet 40 provided at a bottom of the light guide plate 30 and is emitted from the light guide plate 30 to provide back light to a LCD panel 50 disposed on a upper part of the light guide plate 30. As shown in FIG. 2, in the back light unit as described above, a plurality of optical sheets such as a diffusion sheet 31, prism sheets 32 and 33 and a protection sheet 35, etc., may be further provided between the light guide plate 30 and the LCD panel 50.
The back light unit serves to evenly emit light for displaying image on a rear surface of LCD which does not spontaneously emit light. Further, the light guide plate is a kind of plastic formation lens and serves to uniformly transfer light emitted from a light source (LED) to the entire surface of LCD for providing even luminance and lighting to the back light unit. Accordingly, this light guide plate is basically used as an essential element for the back light unit; however, there is a limitation to thinning a thickness of the back light unit due to its own thickness of the light guide plate. Specially, in a case of the back light unit of a large area, an image quality is degraded.